When do you or do you not park up on the curb?

I had this situation happen a while back. I parked out of the way, but up next to the building of a King Soopers while I went in to get some stuff. As I was putting my gear on to leave, a lady passed with her cart and muttered 'Well that's rude.' I didn't think much of it, and really could only agree with her, it is kind of rude. On a different day, I parked my bike in a spot while eating at Chipotle. I witnessed about 7 or 8 cars line up and start pulling into the spot before noticing it was occupied. Too me that also seems rude, to take up a big spot with such a little bike. I'm also afraid somebody (i.e. middle age soccer mom doing 100 things at once) will NOT notice the bike over the hood of her race-striped mini van and plow into my bike.

So, what do you do when running errands?